Investigating the efficacy of potassium silicate and potassium sulfate against the pistachio psyllid (Agonoscena pistaciae) under field conditions

Pistachio (Pistachio vera L.) is an economically valuable crop, and Iran is among the biggest producers and consumers of this product in the world. The pistachio psyllid (Agonoscena pistaciae) is one of the most destructive pests of this crop, resulting in severe damage in terms of yield and quality. Therefore, pistachios are subjected to multiple sprayings with various pesticides during the growing season. As pistachio nuts are exported and largely consumed freshly in Iran, investigating zero-pollution strategies such as applying environmentally safe and non-chemical pesticides to control this pest is essential. In this research, the efficacy of potassium silicate and potassium sulfate against A. pistaciae was investigated in a pistachio orchard and compared with some common pesticides, i.e., acetamiprid, imidacloprid, and thiamethoxam. Pistachios were sprayed with commercial formulations of each pesticide and their recommended dosage and water (control) using a complete randomized block design (CRBD) with three replicates. Populations of A. pistaciae nymphs were evaluated 1 day before and 1, 3, 7, 14, and 21 days following sprayings by randomly collecting 60 leaves from each treatment. Results showed that all pesticides reached their maximum efficacies (>85%) 3 days after spraying, and no significant differences were observed between the compounds (P=0.15). Over time, however, the efficacy of pesticides decreased dramatically, and potassium silicate (37.97%) and acetamiprid (14.58%) showed the highest and lowest efficacies, respectively (P<0.01). Our results suggest acceptable efficacies of potassium silicate and potassium sulfate, as environmentally safe compounds, against the pistachio psyllid compared to common chemical pesticides.